Fused grading shield



Jan. 7, 1936. H FREY 2,027,301

FUSED GRADING SHIELD Filed Sept. 11, 1929 iNVENTOR f1, A? F'kEY ATTORNEY Patented Jan. 7, 1936 UNITED STATES PATENT OFFICE FUSED GRADING SHIELD Application September 11, 1929, Serial No. 391,816

9 Claims. (01. 200-115) The invention relates to protective devices for insulators used in connection with high tension transmission lines and has special reference to grading rings or shields which may be and preferably are employed in conjunction with arcing horns and fuses.

As a preliminary to the disclosure of the invention, it may be well to discuss the situation from a theoretical viewpoint. When a wave, for example a lightning impulse, is travelling along a conductor, half of its energy is in kinetic form and the other half appears as potential or voltage. If the ends of the line are open, then when the wave or impulse reaches the end the kinetic energy is transformed back into potential and the voltage doubles. The wave is then reflected back in the direction from whence it came but as soon as motion begins half of the energy reverts to the kinetic form. If the conductor were to have zero resistance the wave would continue to be reflected back and forth along the line indefinitely. Assuming the line to be grounded at its ends, the energy of the wave on reaching the end will be entirely kinetic in form and the potential or voltage will be zero. In this case the wave is again reflected with equal magnitude but with negative polarity. If the resistance of the conductor is zero the wave will continue to oscillate back and forth along the conductor alternately positive and negative in character. Assuming an instance where a spark gap is at one end of the line, when the front of the wave strikes the gap there is practically the same condition as an open ended line and the wave front is reflected positively. Assuming that there is a break down at an intermediate point on the wave front, the end of the line is immediately grounded and the wave is reflected negatively. If the gap be placed in the middle of the line, then before break down occurs the wave is transmitted just as though no gap were present but as soon as flash-over occurs the line is grounded at this point and the remainder of the wave is reflected negatively. In view of these conditions it will be apparent that if the resistance of the arc and the metallic circuit is zero, the arc-over of a grading shield does not relieve the surge but merely reflects it back, or at least reflects a part of it. If a resistance equal to the surge impedance of the line be placed in series with the are all of the energy of the surge will be relieved and there will be no reflected wave.

It is with all of the above facts in view that I have devised the present invention which has for its general object the provision of a grading shield with arc extinguishing fuses together with an external resistance adapted to act in series with the are so as to relieve all or part of the energy of the surge and entirely avoid or at least reduce the magnitude of the oscillation of the impulse along the line. 5

Another important object of the invention is to provide arc extinguishing fuses adapted to be mounted at the top of a string of insulators and providing electrodes or terminals cooperating with a grading ring at the bottom of the string, 10 it being possible to employ my assembly of arc extinguishing fuses as a replacement for the ordinary type of arcing horns provided at the top of the string in many installations.

A further object of the invention is to provide 15 an arc extinguishing fuse embodying as a part of itself a resistance which will act in series with the are in the event of a flash-over.

A still further object is to provide means whereby the resistance may be utilized in conjunction with the grading shield itself instead of with the fuse while still acting in series with the arc in the event that one takes place.

A more specific object of the invention is to provide a fuse and resistance assembly which may be made as a complete and separate entity adapted to be readily engaged upon the cap of the uppermost insulator unit in a string or chain so that installation may be readily effected in the field.

Another specific object is to provide means whereby the fuses themselves are detachably mounted within their carriersso as to be easily and quickly replaceable when blown.

An additional object is to provide an installation of this character which will be simple and 5 inexpensive to make, easy to apply, positive in action, efiicient and durable in service, and a general improvement in the art.

To the attainment of the foregoing and other objects and advantages, the invention preferably consists in the details of construction and the arrangement and combination of parts to be hereinafter more fully described and claimed, and illustrated in the accompanying drawing in which:

Figure 1 is a side elevation illustrating the invention,

Figure 2 is a top plan View,

Figure 3 is a cross section taken on the line 3-3 of Figure 2,

Figure 4 is a detail longitudinal section through one of the fuses,

Figure 5 is a detail section through one of the fuse holders,

Figure 6 is a side elevation showing the reslstance units associated with the grading ring itself, and

Figure '7 is a top plan view thereof.

Referring more particularly to the drawing the numeral ill designates, rather diagrammatically, a string of insulators comprising any desired or necessary number of units H which may be of any preferred type and connected by any of the well known methods and means to define the string or chain. It is customary that such a string be suspended at its upper end from a toweror other support and that its lower end be equipped with a clamp for supporting a conductor. The tower, clamp and conductor are not shown as such would be unnecessary. Mounted at the lower end of the string in any preferred manner whatsoever is a grading ring 52 which may have any desired detailed construction but which is here represented as comprising simply a circular band with supporting arms it. The present invention is not concerned with the details of this grading ring and any of those known in the art may be utilized.

In carrying out the invention I provide a plurality of fuses indicated broadly by the numeral id and mounted at the upper end of the string it and serving also as electrodes or arcing members.

. It is conceivable that various structures might be provided for mounting these fuses, but in the present instance I have shown a pair of angular plate members it secured in crossed relation as preferably carried by a metal plate iii secured on the underside of the plate members 05 by the same rivets ill or by any other means preferred. The plate members 115 carry holders 2t for the fuses 54, it being intended that the fuses be removably mounted so as to be readily capable of replacement when blown. While the holder might be of different construction from what is shown, each preferably comprises a metal body 2 i mounted as by means of bolts or screws 22 and having a bore or recess 23 within which is received one end of the fuse, the bore having preferably a flaring entrance 2d facilitating insertion of the fuse. A latch device is provided for holding the iuse in place and this may take the form of a leaf spring 25 secured at it upon the metal body and carrying a detent 2i slidable through a slot 28 for cooperation with an element on the fuse.

- 32 adapted to engage behind the detent 2i when the fuse is inserted within the holder. The end of the ferruletd is closed by a cap 33 through which is anchored one end of a rod or wire 36 of high resistance such, for example, as nickel chromium or other resistance alloy. This resistance unit is connected by a fusible link 35 with a metallic stop 35 within the ferrule 39 and tension is applied by a spring 33 located within the ferrule 36 and held under compression. The outer end of the ferrule Si is closed. by a cap 3P.

In installation, it is of course apparent that there may be as many or as few of the fuses provided as may be found desirable though obviously a plurality is of advantage forthe reason that when one fuse blows the others will still continue to afiord protection until all are blown. In the operation it will be clear that the ferrules 30 being in electrical connection by means of the resistance units 34 and links 35 with the angular plates l5 and cap at the top of the insulator string will serve as electrodes or terminals in 5 exactly the same manner as the well known arcing horns. When for any reason, as in the event of lightning, there is a sudden surge along the line tending to produce a. flash-over, an arc will jump from the ferrule 30 of one of the fuses to 10 the grading ring i2. When this takes place the flow of current through the link 35 will cause the same to melt and break, thereby releasing the pressure of the spring 36 and causing the resistance unit 36, spring 36 and cap 33 to be expelled, 16

thereby driving away the arc and preventing it from continuing with the resultant interruption to service. In the event of a subsequent arc another of the fuses will be blown. Naturally, in spection along the line must be and is made from 20 time to time and it can then be readily ascertained which, if any, of the fuses have been blown and those that have been are of course to be replaced by fresh ones. Owing to the high resistance of the units 34 it is apparent that there is 25 proper external resistance in series with the arc to prevent or at least greatly reduce the magnitude of the oscillation of the surge or impulse along the line as explained in the introductory portion of this specification.

if for any reason it is not desired to make use of the fuses, the installation might take the form shown in Figures 6 and 7 wherein I have illustrated high resistances 3T interposed in series between the grading ring 38 and its support 39 35 which is carried by the bottom of the insulator string. In this modification arcing horns of ordinary pattern would be used in lieu of the fuses or ordinary fuses without high resistance elements therein may be employed, the external resistance in series with the arc being provided by the elements 31 which might in actual practice be piles of carbon disks or the like enclosed within insulating containers or holders ifi. It is of course clear that the resistance at this point will operate in the same manner as within the fuses and it is also clear that other locations and arrangments might be resorted to if found advantageous.

From the foregoing description and a study of 50 the drawing it will be apparent that I have thus provided a simply constructed and inexpensive arrangement which will give adequate protection to transmission lines against the consequences of arc-overs. It is thought that the construction, 55 operation and advantages should be readily apparent to one skilled in the art without further explanation.

While I have shown and described the preferred embodiments of the invention, it should 50 be understood that the disclosure is merely an exemplification or" the principles involved as the right is reserved to make all such changes in the details of construction as will widen the field of utility and increase the adaptability or the deas vice provided such changes constitute no departure from the spirit of the invention or the scope of the claims hereunto appended.

Having thus described the invention, I claim:

1. A fuse device of the character described 70 comprising a metallic carrier constructed and adapted to be mounted upon the uppermost inetallic element of a vertical series or insulators, a plurality of holding means mounted upon said carrier, and a fuse removably connected with each id of said holding means and inclined toward the lower end of the series.

2. A fuse device of the character described comprising a metallic carrier constructed and adapted to be mounted upon the cap of the uppermost one of a series of superposed insulators, mounting members on said carrier, and a. fuse removably held by each of said mounting members and inclined downwardly toward the lower end of the series.

3. A fuse device of the character described comprising a metallic carrier constructed and adapted to be mounted upon the cap of the uppermost one of a series of depending suspension insulators, a plurality of socket members on said carrier, and a fuse removably engaged within each socket member.

4. A fuse device of the character described comprising a metallic carrier designed and adapted to be mounted upon the cap of the uppermost one of a series of suspension insulators, a plurality of holding means on said carrier, and a fuse detachably held by each of said holding means and embodying high resistance means, said fuses extending downwardly in inclined position.

5. A fuse device of the character described comprising a metallic carrier designed and adapted to be mounted upon the metallic cap of a vertical series of suspension insulators, a plurality of mounting means on said carrier, and a fuse removably engaged with each of said mounting means and embodying a high resistance element, the fuses radiating from the carrier in downwardly inclined position.

6. A fuse device of the character described comprising a metallic carrier constructed and adapted to be mounted upon the metallic cap of the uppermost one of a string of suspension insulators, socket means mounted on said carrier, a fuse engaged within each socket means and embodying a high resistance element, and means for detachably holding each fuse within the associated socket means, said fuses radiating from 5 said carrier in a downwardly inclined position.

7. A fuse device of the character described comprising a metallic carrier adapted to be mounted upon the cap of the uppermost insulator in a string of suspension insulators, a plu- 10 rality of socket members mounted upon said carrier and equipped with latch means, and a fuse removably engaged within each socket member and having means cooperating with said latch means. 15

8. A fuse attachment for a string of insulators, comprising a metallic carrier of plate-like formation formed for engagement upon the metal cap of the uppermost unit in a string of insulators, a plurality of metallic socket members mounted on 20 said carrier, spring latches on said socket members, and elongated fuses having terminal ferrules removably engaged within the respective socket members, the ferrules having outstanding beads cooperating with said latch members. 25

9. An arc disrupting device comprising a cruciform metallic carrier constructed and designed for mounting upon a metallic cap of the uppermost one of a string of suspension insulators, the cap having a suspension element thereon and said :0 carrier being apertured to accommodate said suspension element, said carrier including downwardly and outwardly inclined radial arms, a socket on each of said arms, a fuse disposable within each socket, and means for latching each fuse within its socket, said fuses radiating from the carrier in a downwardly inclined direction.

HOWARD ALBERT FREY. 

